Inconsistent initialization of RoPE embedding across component builders

[Ankur-singh]

Context

The Llama 3.1 self-attention builder takes RoPE embeddings as an argument, allowing us to build RoPE a single time across all layers. However, the corresponding components for Llama2 and Llama3 do not do this -- they instead construct RoPE for every single layer.

Whether we should use a single global RoPE vs one RoPE per layer? We should standardize this.

Originally posted by @ebsmothers in #2282 (comment)